The present invention relates to a device for treating a paper web or a sheet of paper prior to being printed. The paper is treated in a calender roller pair upstream of the first printing unit.
A device for treating a paper web prior to printing is known from DE 21 61 322 C3. In this device, the paper web is subjected to a pre-pressing process by means of a pair of drawing rollers in order to keep the paper web stable during printing.
The drawing rollers of this prior device have an at least small difference in circumferential speed in comparison with the cylinders of the successive print units. By means of this, it is intended to remove possible paper dust or particles which may be loosely attached to the paper web prior to the web entering the first print unit. A dampening agent unit can be placed against each drawing roller.
DE 196 17 601 A1 describes a method for printing and upgrading webs, wherein the running web is satinized and subsequently printed without intermediate winding.
DE-PS 245 182 shows a paper web, which is satinized between the lacquering and printing processes.
U.S. Pat. No. 2,147,421 discloses calender rollers, wherein one of the calender rollers is driven by means of an rpm-controlled electric motor.
The object of the present invention is based on providing a device for treating a paper web or a sheet of paper prior to printing.
In accordance with the present invention, this object is attained by providing a calender roll pair upstream of the first printing unit. At least one of the calender rollers of the pair is driven by its own relative position-regulated electric motor. A paper web tension regulating device may be arranged between the calender roller pair and a first printing unit. The first print unit may accomplish offset printing with xe2x80x9cwaterlessxe2x80x9d planographic printing formes.
The advantages which can be achieved by the present invention in particular rest in that it is not necessary to assign additional mechanical aids or dampening water to the pair of calender roller in order to make the paper dust, or any others of those particles adhering to the paper web, ineffective. The quality of the material to be printed is improved by the compacting process, so that it is possible to use a material to be printed which is of lesser quality.
The method can be advantageously employed in connection with dry offset printing processes, wherein a cleaning effect of the printing plate by means of the dampening units is omitted. Moreover, in an advantageous manner, a regulating device for regulating the paper web tension is arranged between the pair of calender rollers and the first print unit. This regulating device is provided to be able to compensate for fluctuations in the tension of the paper web caused by the calendering process.